1. Field of the Invention
The present invention relates generally to apparatus for detecting the authenticity of a coin, and more particularly, to a compact and inexpensive electronic coin verification apparatus which electronically compares a coin under test to a reference coin.
2. Description of the Prior Art
Vending machines and other coin operated mechanisms typically include an apparatus for analyzing coins inserted within such machines for the purpose of determining whether such coins are authentic and of the proper monetary value to actuate the machine. Mechanical coin verification apparatus is known in the art wherein the size and/or weight of inserted coins are mechanically determined to detect counterfeit coins or coins of the wrong monetary value. Often, such mechanical apparatus includes a magnet for attracting ferrous metal slugs and thereby preventing such slugs from actuating the machine. However, such mechanical coin verification apparatus is subject to numerous disadvantages, including jamming due to bent coins, slow coin feed rates, relatively large size, relatively great expense, and difficulty in altering such apparatus to detect coins of a different value.
Electronic coin detection apparatus is also known to the art. In one type of such electronic coin verification apparatus, the coin under test is used to modulate the frequency of a first oscillator, the output frequency of which is then compared to the output frequency of a second reference oscillator. However, coin verification apparatus of this type is sensitive to changes in temperature and supply voltage, since such changes often affect the first and second oscillators to a different extent. Accordingly, frequent adjustments are typically required to maintain such coin verification apparatus in working order. Moreover, alteration of such apparatus to detect coins of different values requires either replacement of components or substantial adjustments to the reference oscillator. In addition, coin verification apparatus of this type is generally bulky and expensive.
A second type of electronic coin verification apparatus is also known in the art wherein a reference coin, of the type to be detected by the coin verification apparatus, is stored within such apparatus, and a comparison is made electronically between a coin under test and the stored reference coin. For example, in U.S. Pat. No. 2,589,214, an electrical coin selector is disclosed wherein a standard coin lies adjacent a first winding of an E-shaped iron core, while the coin under test is temporarily held against a second winding thereof. A third central winding of the iron core has a voltage induced therein through inductive coupling between it and the first and second windings of the E-shaped core. A null voltage across the third winding indicates a balanced condition wherein the standard coin and coin under test have the same characteristics. Similarly, in U.S. Pat. No. 3,059,749, a coin testing apparatus is disclosed wherein a detector bridge circuit includes a pair of coil form inductors, one of which surrounds a standard coin while the other surrounds a slot through which a test coin is guided. The bridge circuit includes a pair of output terminals which are balanced or nulled when the coin under test matches the standard coin. Trimmer capacitors are provided within the bridge circuit to provide for adjustment of the bridge circuit to provide a null output signal during balanced conditions.
However, prior art coin verification apparatus utilizing a standard or reference coin is relatively bulky and expensive, prohibiting its use in such applications as table-top electronic games and other compact, cost-sensitive equipment.
Accordingly, it is an object of the present invention to provide an electronic coin verification apparatus adapted to accept coins at a relatively rapid feed rate.
It is another object of the present invention to provide an electronic coin verification apparatus which is extremely compact and of inexpensive construction.
It is still another object of the present invention to provide an electronic coin verification apparatus which is relatively immune to changes in temperature and supply voltage.
It is a further object of the present invention to provide an electronic coin verification apparatus wherein the type of coin which the apparatus is to detect may be easily and conveniently altered.
These and other objects of the present invention will become more apparent to those skilled in the art as the description thereof proceeds.